don't know jack

:screwy: Pulled OEM stereo out of my '01 cc. In addition to the main plug on the back there's an unused port between it and the antennae plug. Anyone know what this is for?

Thx

External cd player? does it have a cd player built in?

Or it might be OnStar

yep, has internal cd, no to on-star

Well it might be where OnStar would go if you had it.

It's probably for the tape deck. I have the factory tape deck in the console. When I installed my Sirius in my '00 there was a plug in the port. When I unplugged that harness from the radio it still worked so I assume it was for the tape deck.

Its for a cd changer. All the factory head units have this output whether or not there is a changer in the vehicle. Whats cool about this is you can get an adapter that plugs into this port that gives you a set of auxillary inputs for things such as satellite radio, ipods, ets.